Features

Dr. William (Bill) Farrell, Scientist, Lunar Exploration Program

Dr. Farrell: Sure. The LEAM – Lunar Ejecta and Meteorites – was an experiment designed to detect accelerated small particles, especially those originating from micro-meteorite impacts. But as it turned out, one of the things it detected, particularly when the experiment crossed the lunar terminator, is hyper-charged dust, and the dust seemed to be moving relatively fast. The dust seemed to be moving at 100 – 300 meters per second, but the exact speeds couldn’t quite be differentiated in the instrument. This dust activity was really an unexpected find! And this was found at the terminators. The reason why the terminators are interesting is because that’s where electric fields have been found to be the strongest and largest on the Moon, so there’s a strong suspicion that this lunar dust that’s accelerated is tied to the lunar electrical environment.

Now what we want to do, of course, is to really follow through on that and not only have a dust detector – and maybe a slightly more sensitive dust collector – but also carry with that an electric field package and a plasma package, because the electric fields are actually established by the incident plasma and the nearby boundary. So in Otto Berg’s case, he got the when and where, but what we’re trying to do is actually get the when, where, and why by getting the full electrostatic picture. So it’s a combined suite: dust detection, DC E-field sensor, and plasma spectrometers.

NTB: How far along are you on development of the new instrument?

Dr. Farrell: Well, you know, a lot of these instruments already have heritage. They’ve already flown, or the concepts have already been tested in other places. For example, the DC E-field sensors are commonly flown in space plasma applications in the ionosphere and the magnetosphere, and we’re teaming with the University of California at Berkeley, who are the world’s preeminent experts in that area. They’re awesome.

The plasma spectrometers, we’ve been building them here at Goddard, and other places out in the community have been building these spectrometers for years and years. Really, since the dawn of the space age, since the early 1960s. So they’ve been really honed down. Probably the biggest challenge we have is miniaturization to a landed system, but this technology exists. A lot of it’s already out there; it’s how you package it. That’s really the issue.

NTB: So that basically is your group’s job now?

Dr. Farrell: That’s right. Packaging – how would you get it into a lander, accommodations, those kinds of issues. We do have some experience with this because back in 1999 we proposed putting an atmospheric electricity package on what was the Mars 03 Surveyor mission. I don’t know if your readers would be interested in the convoluted history of the Mars 03 Surveyor Mission, but basically the way it worked was prior to the MER – the two exploration rovers – the Mars Program was going to have a Mars 03 lander and sample return. This was back when there was this really aggressive push for relatively cheap missions to Mars. But this lander was a powered lander system that had heritage back to the Mars Polar Lander, which, of course, failed. After the failure, the Young commission pointed out to NASA that more money needed to be spent on Mars missions to buy down risks. Because of this new view, both the Mars 01 and Mars 03 missions developed with a leaner but riskier approach were considered suspect and replaced with the two MERs, which have been hugely successful. The MERs also avoided challenging powered landings by using the bouncing balloon system, which is probably not the technical name for it, but you know what I mean.